Work will continue on the properties of DNases and DNase inhibitors in L1210 cells of the mouse and their relation to cellular proliferation. Of particular interest are the functions of actin (DNase I inhibitor) as a DNase inhibitor and the mechanism of regulation (if any) of its activity. The relationship of different forms of actin to DNase inhibition will also be studied as well as the distribution and amounts of DNases and inhibitors in normal and leukemic cells.